1. Field of the Invention
The present invention generally relates to a syringe and, more particularly, to a syringe that can contain and separate two substances and can mix the two substances before injection.
2. Description of the Related Art
Referring to FIG. 1, Taiwanese Patent No. 146251 discloses a syringe 9 including a tube 91, a first partitioning member 92, a second partitioning member 93 and a plunger rod 94. The tube 91 has a nozzle 911 on one end thereof. The first partitioning member 92 and the second partitioning member 93 are received in the tube 91 but spaced from each other. The plunger rod 94 is arranged on the other end of the tube 91. In such an arrangement, the tube 91 will form a first chamber 912 between the nozzle 911 and the first partitioning member 92, a second chamber 913 between the first partitioning member 92 and the second partitioning member 93, and a third chamber 914 between the second partitioning member 93 and the plunger rod 94. The first chamber 912 contains a first drug 81 and the third chamber 914 contains a second drug 82. The tube 91 further includes a by-pass passage 915 having an entrance 916 and an exit 917. The first partitioning member 92 further includes an annular groove 921 and a plurality of axial grooves 922, each having one end communicating with the annular groove 921 and the other end communicating with the first chamber 912.
When the syringe 9 is in use, a user can push the second drug 82, second partitioning member 93 and first partitioning member 92 towards the nozzle 911 by pushing the plunger rod 94. Meanwhile, when a face 931 of the second partitioning member 93 reaches the entrance 916 of the by-pass passage 915, the annular groove 921 will communicate with the exit 917 of the by-pass passage 915. Thus, the second drug 82 in the third chamber 914 will flow into the annular groove 921 of the first partitioning member 92 via the by-pass passage 915. The second drug 82 then enters the first chamber 912 via the axial grooves 922 to mix with the first drug 81.
However, it is difficult to manufacture the syringe 9 as the syringe 9 requires forming the by-pass passage 915, annular groove 921 and axial grooves 922. This significantly increases the manufacturing costs thereof. Especially, it is not economic to manufacture a disposable syringe 9 that is used only once.